PROJECT SUMMARY This project proposes to study hypothermia as a treatment of refractory status epilepticus (RSE). RSE is an increasingly common problem in VA Intensive Care Units. This may be due to improvement in life support systems and ICU technology, to increased availability of EEG recordings and increased recognition of subtle status epilepticus (SE) and other factors. The results of treatment of RSE are very poor, with high mortality and morbidity. New treatments are needed. Deep hypothermia (200 C) is used clinically during cardiac surgery and neurosurgery. Moderate hypothermia (32-330 C) is used routinely in the treatment of neonatal hypoxic- ischemic encephalopathy, of post-cardiac arrest encephalopathy and of traumatic brain injury. Hypothermia has proved safe and effective in those conditions. It has also been shown to inhibit seizure activity. Yet, it is rarely used to treat RSE, and we lack a basic understanding of its indications and effectiveness in RSE. We will test the hypothesis that deep hypothermia reduces seizure activity in two models of experimental status epilepticus induced respectively by chemical (lithium and pilocarpine) or by electrical (perforant path) stimulation of the brain. We will compare deep and mild hypothermia, and will test different durations of mild hypothermia, to find out whether longer durations of mild hypothermia can be as effective in terminating RSE as short durations of deep hypothermia. We will compare two methods for delivering hypothermia: whole body cooling and head cooling (cool cap). For the same level of cooling of parietal cortex, we expect whole body cooling is more effective than the cool cap method in terminating SE. Finally, we will study the effect of hypothermia treatment on the long-term consequences of RSE: neuronal injury, blood-brain barrier breakdown, cell-mediated inflammation, epileptogenesis and behavioral deficits. We expect hypothermia treatment to reduce all of these complications. At the end of this study, we expect to be able to define the depth, duration and method of hypothermia that is most effective in the treatment of experimental status epilepticus.